This invention relates to a method of combinatorially weighing a mixture and, more particularly, to a combinatorial weighing method which employs a single combinatorial weighing unit and a single automatic weighing unit having two or more counter mechanisms for providing an article mixture, wherein the various article categories are incorporated in the mixture at a desired target ratio in terms of the number of articles in each category, while the total weight of the mixture is that which is equal or closest to a target weight value.
It is common practice to adopt so-called combinatorial weighing and combinatorial counting in order to weigh and count articles with great accuracy.
When it is desired to obtain a batch of articles of a target weight through combinatorial weighing, n-number of weighing machines are supplied with the articles, wherein there is a small difference in the weight supplied from one machine to the next. Each weighing machine separately weighs the group of articles supplied to it, all possible combinations of the resulting weight values are found and the sum of the weight values in each and every combination is computed. Then, from among all combinations found, there is selected one combination the sum of whose weight values is equal to a target weight or closest to the target weight within preset allowable limits. Articles are discharged from those weighing machines belonging to this selected combination, thereby providing a batch of articles of the target weight.
When it is desired to obtain a batch of specified articles of a target number through combinatorial counting, n-number of weighing machines are supplied with the articles, wherein there is a small difference in the weight supplied from one machine to the next. Each weighing machine separately weighs the group of articles supplied to it, each resulting weight value is divided by the unit weight of the articles to provide the number of the articles in each weighing machine, all possible combinations of the resulting numbers are found and the sum of the numbers in each and every combination is computed. Then, from among all combinations found, there is selected one combination the sum of whose numbers is equal to a target number or closest to the target number within preset allowable limits. Articles are discharged from those weighing machines belonging to this selected combination, thereby providing a batch of articles of the target number.
The above-mentioned combinatorial weighing and counting methods are applicable to articles of a single variety or to a mixture of different articles where the ratio of the various categories of articles in the mixture is predetermined. While the articles can be weighed and counted with great accuracy in both cases, it has not been possible to obtain a mixture of plural categories of articles wherein the number ratio of the article categories constituting the mixture takes precedence over the overall target weight. More specifically, in a case where it is desired to set (a) a target number ratio for the article categories constituting the mixture (in other words, where it is desired to acquire a specific number of articles in each category), (b) the total weight (target weight) of the mixture and (c) the total number (target number) of all the articles constituting the mixture, it has not been possible to obtain a mixture wherein the articles in each category are contained in the mixture at the number ratio equal or closest to the target number ratio and, at the same time, wherein the mixture has a total article number or total weight equal or closest to the target number and target weight, respectively.
It has been proposed, therefore, to provide one counting mechanism for each category of articles, count out the number of articles in each category on the basis of the target number ratio, discharge the articles in the numbers counted out by each counting apparatus, and gather these discharged articles into a mixture. Although the number ratio of the various articles constituting the mixture and the total number of the articles in the mixture can be brought into agreement with the respective target values by employing the proposed method, the mixture so obtained will not satisfy the target weight requirement.